Microgrid Controls

NREL researchers develop and test microgrid controls at multiple time scales. This
work has been demonstrated via in-house modeling and hardware development as well
as testing of partner-developed systems.

A microgrid is a group of interconnected loads and distributed energy resources that acts as
a single controllable entity with respect to the grid. It can connect and disconnect
from the grid to operate in grid-connected or island mode.

Microgrids can include uncontrollable loads as well as distributed energy resources
such as generators, storage devices, and controllable loads. Microgrids generally
must also include a control strategy to maintain, on an instantaneous basis, real
and reactive power balance when the system is islanded and, over a longer time, to
determine how to dispatch the resources. The control system must also identify when
and how to connect/disconnect from the grid.

Capabilities

Modeling and simulation of microgrid systems on timescales of electromagnetic transients
and dynamic and steady-state behavior

Controller hardware-in-the-loop testing, where the physical controller interacts with
a model of the microgrid and associated power devices

Expertise in distributed optimization and control of sustainable power systems that
can be applied to microgrid distributed energy resources dispatch

Projects

NREL is partnering with the Electric Power Research Institute to validate the performance
of a Spirae-developed advanced microgrid controller capable of managing 1–10 MW of
aggregated generation capacity. The aim is to develop a commercially viable and flexible
microgrid controller that can easily adapt to end-user applications and electric grid
characteristics.

The Electric Power Research Institute is leading a team that includes Spirae, NREL,
a microgrid system analytics consultant, 14 utilities, and three target communities.
NREL’s role is to validate and test the functions of the controller by connecting
it to a virtual model of a microgrid embodied within a real-time digital simulator.
The controller is also being connected to a utility-scale battery inverter, which
interacts with the virtual model through an AC power amplifier and adjusts its output
to the simulated electrical grid demand.

This project investigates the interaction of distribution management systems with
local controllers, including microgrid controllers. The project is developing integrated
control and management systems for distribution systems to address high penetrations
of interconnected distributed energy resources. The integrated control will be demonstrated
using controller and power hardware connected to a simulation of a distribution system
that contains a microgrid.

Omnetric and partners have developed a distributed intelligence platform that can
support utility grid and microgrid operations. Power management during microgrid operation
is enabled by the Siemens Microgrid Management System. NREL will test the Microgrid
Management System performance on a microgrid test platform at its Energy Systems Integration
Facility. The platform will include distributed equipment including a microgrid switch, PV inverter, wind
power inverter, diesel generator, controllable loads, metering, and a grid simulator
to emulate the point of common coupling.

NREL researchers have developed and tested advanced inverter control algorithms that
“self-synchronize” when a utility voltage is not present. Under loss of utility power,
a microgrid must regulate voltage and frequency within the grid. This research uses
virtual oscillator control theory to implement voltage and frequency regulation.

NREL piloted a dual-stage competitive procurement process, where ESIF engineers ran
microgrid controllers from multiple vendors through several challenging power systems
and cybersecurity performance evaluations. Following the rigorous 21-week program,
NREL purchased a microgrid controller from Schweitzer Engineering Laboratories, resulting in a more comprehensive microgrid research platform. Controllers were
evaluated against eight key performance parameters to measure a range of functions
from power quality and reliability to the use of renewable versus fossil fuel generation.